Image processing techniques of acquiring two-dimensional information of an object to be measured, and estimating three dimensional information of the object based on the two-dimensional information have been known.
According to a first image processing technique, when performing a matching operation between two images acquired from an object to be measured, highly precise matching result may be acquired in a short period of time (for example, Japanese Laid-open Patent Publication No. 2006-331108). According to the first technique, in stereo measurement using Dynamic Programming (DP) matching, an area where there is no change in the luminance values of corresponding pixels between frames succeeds the route searching result of the preceding frame. An area where there is no change in the luminance values of corresponding pixels between adjacent scanning lines in one frame processing succeeds the route searching result of the just preceding scanning line.
According to a second technique, for example, in searching a feature point of an object on an epipolar line of a second image, false detection is checked while calculating a distance from a first camera to the object with high accuracy (for example, Japanese Laid-open Patent Publication No. 2013-257289). According to the second technique, an image processing device acquires a first image formed by imaging a workpiece with a main camera, and a second image formed by imaging the workpiece with a sub camera having a line of sight different from the main camera. Then, the image processing device searches on an epipolar line of the second image, to specify a feature point of the workpiece on the second image, and calculates a distance to the workpiece by stereo method. At this time, based on the number of pixels of a feature quantity of the workpiece stored in advance in the storage device and the distance to the workpiece, an approximate value of the distance between the main camera and the workpiece is calculated from the number of pixels of the feature quantity of the workpiece in the first image. Then, according to the approximate value of the distance, the image processing device sets a search range for searching a feature point of the workpiece on the epipolar line in the second image so as to narrow the search range.
According to a third technique, for example, a position of a feature in the periphery of a road is measured (for example, Japanese Laid-open Patent Publication No. 2009-75117). According to the third technique, an image with the photographed periphery of the road is stored in an image storage part. A three dimensional point group model storage unit stores a point group indicating three dimensional coordinates obtained by laser measurement executed simultaneously with the photographing of the image, as a road surface shape model. A model projection part projects the point group onto the image, and an image display part displays the image and the point group superimposed together on a display. A user assigns a pixel on a measuring-objective feature as a measuring image point by an image point input part. A vicinity extracting part extracts a point positioned in the vicinity of the measuring image point and superposed with the measuring-objective feature, from the point group. A feature position calculating part outputs the three dimensional coordinates indicated by the extracted point, as the three dimensional coordinates of the measuring-objective feature.